In a conventional injector (U.S. Pat. No. 5,350,119), provision is made in a valve seat member for an outlet orifice, which is closed by a valve needle, serving as a closing body. Viewed from the flow direction of the fuel, a spray-orifice plate having a spray orifice is arranged behind the outlet orifice, said spray orifice constituting the narrowest flow cross-section in the fuel flow path through the valve and, thus, defining the quantity of spray-discharged fuel, given a certain fuel pressure and duration of opening.
Another conventional injector (European Patent No. 0 328 550) has a pot-shaped valve body, in whose base a guide bore is provided for a valve needle. On the outlet side, provision is made at the base of the valve body for a conical projection extending into a similarly conical cutout in a valve seat member, such that between the valve body and the valve seat member a hollow-cone-shaped swirl or spin chamber is formed, whose tip discharges into a spray orifice, which functions as a metering orifice, and which can be closed by means of the valve needle, guided in the valve body.
In the base of the valve body, distributed around the guide bore, fuel channels are arranged which are tilted and staggered with respect to an axis of rotation of the swirl chamber such that the fuel flowing into the swirl chamber has a speed component in the circumferential direction. In this way, the goal is for the fuel to be spray-discharged, essentially, in the form of a closed hollow cone and to be atomized in the combustion chamber of an internal combustion engine.
In another conventional injector (U.S. Pat. No. 5,307,997), provision is made, in a valve seat member having a spray orifice, for a conical depression into which extends a valve body guiding a valve needle and having a corresponding conical projection. In this way, between the valve body and the valve seat member, a swirl chamber is created, which is located in front of the spray orifice, with respect to the direction of flow.
The fuel is fed into the swirl chamber through fuel channels which are tilted and staggered with respect to an axis of rotation of the swirl chamber, such that the fuel arriving in the swirl chamber has a speed component in the circumferential direction.
The fuel channels comprise a first bore segment, which has a relatively large diameter and relatively great length, and to which is joined, on the outlet side, a bore segment having a reduced diameter and relatively short length. The bore segments having a reduced diameter together constitute the narrowest cross section, necessary for fuel metering, in the flow path through the injector.
Also, in the case of this, conventional injector, the fuel is spray-discharged in the form of a uniform, closed, hollow-cone-shaped fuel lamina.